Showing papers on "Circular polarization published in 1973"
TL;DR: There are at least three different definitions of cross polarization used in the literature, and the definition which corresponds to one standard measurement practice is proposed as the best choice.
Abstract: There are at least three different definitions of cross polarization used in the literature. The alternative definitions are discussed with respect to several applications, and the definition which corresponds to one standard measurement practice is proposed as the best choice.
895 citations
357 citations
TL;DR: The measured circular dichroism of a light-scattering specimen may be highly sensitive to light-detection geometry of the instrument, and whether differential light scattering arises may depend upon the presence or absence of ordered asymmetry in the organization of the scattering particle.
Abstract: Experimental techniques are presented that can be used to assay and correct for differential light scattering effects in circular dichroism spectra of biological macrostructures. The assay is based upon use of variable detector geometries that collect light over large solid angles. Disrupted T2 virus suspensions and purified T2 phage DNA exhibit geometry-independent spectra; the spectrum of intact T2 virus is highly sensitive to detection geometry. On the basis of spectra obtained after light-scattering correction, the structure of T2 DNA in the phage particle is assigned to the C form. We conclude that: (i) The measured circular dichroism of a light-scattering specimen may be highly sensitive to light-detection geometry of the instrument. This effect is indicative of differential scattering intensity for left and right circularly polarized light. (ii) Some optically active particles, although they scatter light intensely, exhibit circular dichroism that is independent of detection geometry and, therefore, apparently uninfluenced by differential light scattering. We infer that whether differential light scattering arises may depend upon the presence or absence of ordered asymmetry in the organization of the scattering particle. (iii) The circular dichroism of any light-scattering specimen should be measured again in apparatus designed for differential light-scattering correction as a prerequisite to meaningful structural conclusions. (iv) Differential scattering effects in circular dichroism may be potentially useful as a probe for large-order organization of the scattering particle.
72 citations
TL;DR: In this article, it has been suggested that Rayleigh and Raman scattered light from optically active molecules should show polarization effects which could provide new information about their structure and configuration.
Abstract: IT has been suggested that Rayleigh and Raman scattered light from optically active molecules should show polarization effects which could provide new information about their structure and configuration1–3. Circular intensity differentials (CIDs) defined by2
where IR and IL are the scattered intensities in right and left circularly polarized incident light, have recently been observed in the Raman spectra of α-phenylethanol and α-phenylethylamine4. (Raman CID was first reported by Bosnich et al.5, using α-phenylethylamine, but it has been suggested that the results are spurious4.) Observations now reported on another liquid, α-phenylethylisocyanate, could indicate that these differentials originate in bending vibrations around the asymmetric carbon atom.
59 citations
TL;DR: In this article, the authors make a calculation of the gyro-synchrotron emission in moving type IV sources in the solar corona, showing that most moving sources have the following features: (1) a rather strong magnetic field, ≈ 10 G, is carried out within the source, which is required to achieve high degree of circular polarization often observed.
Abstract: Calculations of the gyro-synchrotron emission are made for conditions which might be expected in moving type IV sources in the solar corona. Two simple models for an evolving source are treated: a uniform cube and an inhomogeneous sphere. The results suggest that most moving sources have the following features: (1) A rather strong magnetic field, ≈ 10 G, is carried out within the source. This is required to achieve the high degree of circular polarization often observed. (2) Synchrotron self-absorption causes the source to be optically thick at frequencies less than about 100 MHz, thus restricting the bandwidth of the radiation. The self-absorption decreases as the source moves outward and expands. The turnover frequency, which separates the optically thick and thin spectral regimes, moves rapidly to lower frequencies, accompanied by a change from low to high circular polarization. In the case of an inhomogeneous source, the source appears to be larger at the lower frequencies. (3) Razin-Tsytovich suppression cannot be an important factor in determining the characteristics of most sources.
57 citations
TL;DR: In this article, it was shown that multiphoton ionization of unpolarized atoms with circularly polarized light can lead to the production of highly polarized electrons, and the connection of this effect with the Fano effect in single-photon ionization was discussed.
Abstract: It is shown that multiphoton ionization of unpolarized atoms with circularly polarized light can lead to the production of highly polarized electrons. The connection of this effect with the Fano effect in single-photon ionization is discussed.
54 citations
TL;DR: In this paper, the general properties of the emission from distributions of particles with small pitch angles are discussed, and the emissivities and degrees of polarization for several specific source models are presented.
Abstract: Some of the features of synchrotron radiation are examined which occur when relativistic particles move at small pitch angles in a magnetic field. The emission from individual particles is computed. The general properties of the emission from distributions of particles with small pitch angles is discussed, and the emissivities and degrees of polarization for several specific source models are presented. For sources which mainly contain particles with small pitch angles, the degree of circular polarization will normally be high, whereas, if the magnetic field is somewhat irregular, the degree of linear polarization will be small. If the particle distribution also has a low-energy cutoff, the emissivity will vary linearly with frequency at low frequencies.
50 citations
TL;DR: In this article, an apparatus is described for measuring Raman backscattering with both linearly and circularly polarized light, which can be directly compared and used to determine the relative magnitudes of the three invariants of the non-symmetric Raman tensor for randomly oriented molecules.
Abstract: An apparatus is described for measuring Raman backscattering with both linearly and circularly polarized light. All four polarization components, parallel, perpendicular, corotating and contrarotating, can be directly compared and used to determine the relative magnitudes of the three invariants of the non-symmetric Raman tensor for randomly oriented molecules. The method has been applied to the resonance Raman spectrum of ferrocytochrome c. Antisymmetric scattering, previously detected through anomalous depolarization ratios, has been confirmed by direct measurement of the antisymmetric tensor invariant. In addition to the four anomalously polarized bands, two bands with normal polarizations have been shown to exhibit significant antisymmetric scattering. This result implies a reduction from four-hold symmetry for the heme chromosphere.
47 citations
TL;DR: In this article, a perturbation solution for a vibronic model for the relaxed excited state of the $F$ center, in the limiting case of weak electron-phonon coupling, was given.
Abstract: A perturbation solution is given for a vibronic model for the relaxed excited state of the $F$ center, in the limiting case of weak electron-phonon coupling. The resulting predictions of the model are compared with available data on radiative lifetimes, Stark effects, magnetic circular polarization, and stress-induced polarization of $F$-band luminescence in alkali halides. It is shown that a consistent quantitative interpretation of most of these data is possible on this basis if the $2s$ electronic state lies below the $2p$ state in the relaxed cubic configuration by an energy difference which is \ensuremath{\sim} 0.09 eV for KCl and \ensuremath{\sim} 0.15 eV for KF. The long radiative lifetime should then be attributed predominantly to the $2s$ state being only weakly coupled to the $2p$ state by the phonons, rather than to spatial diffuseness of the $2p$ state. The model also accounts for the observed ratio of the electric-field-induced change in the radiative lifetime to the field-induced polarization of the luminescence, for the temperature dependence of the radiative lifetime and field-induced polarization, and for the absence of any such temperature dependence in the stress-induced polarization.
47 citations
TL;DR: The invariants of the Raman tensors of eight strong Raman active vibrations of ferrocytochrome c have been determined using both linearly and circularly polarized light at 5145 A. The relative intensities of the perpendicular, parallel, contrarotating and co-rotating components have been measured and analysed by the method of McClain to obtain the symmetry assignment of each of these vibrations; the symmetry group of the heme is believed to be Cs showing a plane of reflection as the only symmetry element as mentioned in this paper.
Abstract: The three invariants of the Raman tensors of eight strong Raman active vibrations of ferrocytochrome c have been determined using both linearly and circularly polarized light at 5145 A. The relative intensities of the perpendicular, parallel, contrarotating and co-rotating components have been measured and analysed by the method of McClain to obtain the symmetry assignment of each of these vibrations; the symmetry group of the heme is believed to be Cs showing a plane of reflection as the only symmetry element. Since the lowering of the symmetry of the heme group is due to hemeprotein interactions, Raman Polarization measurements appear to offer a new probe for obtaining the strength of such interaction.
44 citations
TL;DR: In this paper, the generation of circular polarization in the process of transfer of radiation within a compact source, due to the presence of relativistic electrons, is discussed, and the interpretation of the observations of polarization of compact radio sources in terms of this mechanism (called circular repolarization'') yields the values of 1 to 10 for the lower limit of the ratio of relatvistic to cold electron densities.
Abstract: Generation of circular polarization in the process of transfer of radiation within a compact source, due to the presence of relativistic electrons, is discussed. The interpretation of the observations of polarization of compact radio sources in terms of this mechanism (called circular repolarization'') yields the values of 1 to 10 for the lower limit of the ratio of relativistic to cold electron densities. (auth)
TL;DR: In this article, it was shown that both the longitudinal Goos-H\"anchen shift and the new transverse shift are quantized, each having two eigenvalues and two Eigenfunctions, which are the principal linear polarization states in the first case and the circularly polarized state in the second case.
Abstract: In additional measurements following their experimental demonstration of the now well-known longitudinal shift of a light beam undergoing total reflection, Goos and H\"anchen have observed that an incident beam of natural light is separated into two beams with polarizations normal and parallel to the incidence plane. Although an explanation of this filtering effect of orthogonal modes is easy in terms of either the Artmann or the Renard formulas of the Goos-H\"anchen shift, which are deduced from a stationary phase and an energy-conservation argument, respectively, it seems that this explation has not yet been produced. We describe here associated theoretical and experimental work showing that both the longitudinal Goos-H\"anchen shift and the new transverse shift are quantized, each having two eigenvalues and two eigenfunctions, which are the principal linear polarization states in the first case and the circularly polarized states in the second case. Thus the longitudinal and the transverse shifts should not be simultaneously observable. This can be justified in terms of the so-called tangential and sagittal focal lines produced by total reflection from a point source. Our theoretical reasoning is based on formal properties of Poynting's energy-flux vector. Our experiments consist of (1) a confirmation, with photographic recording, of the Goos-H\"anchen "polarization effect," (2) a similar demonstration of the filtering of the two circular polarization modes by observation of the transverse shift. In the latter case our apparatus is similar to the one we have used for demonstrating the transverse shift, but with the circular polarization analyzer placed after rather than before the totally reflecting prism. Our new measurements also comprise an improved evaluation of the transverse shift.
TL;DR: In this article, the Kirchhoff method and the small perturbation method are used in combination in the composite model of rough-surface wave scattering, and they are shown to be identical to the first order for scattering by a perfectly conducting body of a circularly polarized incident wave into a scattered wave polarized in the expected sense of circular polarization.
Abstract: The Kirchhoff method and the small perturbation method are usually used in combination in the composite model of rough-surface wave scattering. They are shown to be identical to the first order for scattering by a perfectly conducting body of a circularly polarized incident wave into a scattered wave polarized in the expected sense of circular polarization. Thus for this case, a single application of the Kirchhoff method is as accurate as the composite model and is simpler to apply. The identity remains valid for arbitrary directions of incidence and scattering, but not for other polarizations. Statements in the literature at variance with these results appear to be based on derivations which neglect some part of the complete solution.
Patent•
04 Jan 1973
TL;DR: In this article, a dipole is mounted on one side of an insulating substrate and a narrow conductor is formed on the other side substantially opposite the dipole, with part of the Dipole, the substrate, and the conductor together forming a stripline feed which may have a matching network formed by a further part of dipole.
Abstract: Aerial for receiving or transmitting circularly polarized electromagnetic radiation includes a dipole mounted substantially within the aperture of a slot and means for coupling the slot to the dipole asymmetrically. It may also include an electromagnetic cavity adjacent the coupled dipole and slot. In one embodiment the dipole is formed on one side of an insulating substrate and a narrow conductor is formed on the other side substantially opposite the dipole, with part of the dipole, the substrate, and the conductor together forming a stripline feed which may have a matching network formed by a further part of the dipole, the substrate, and the conductor.
TL;DR: In this paper, the photon energy dependence of the circular polarization efficiency and angular distribution of ejected electrons were calculated for Li, Na and K atoms, and the ratio of the two-photon ionization probability with circularly polarized photons to that with linearly polarized photons was calculated.
Abstract: The photon energy dependence of the circular polarization efficiency (i.e. the ratio of the two-photon ionization probability with circularly polarized photons to that with linearly polarized photons) and the angular distribution of the ejected electrons are calculated for Li, Na and K atoms.
TL;DR: The theory of multiphoton ionization for an atomic system of arbitrary complexity is developed using a density matrix formalism in this article, where an expression is obtained which determines the differential N-photon ionization cross section as a function of the polarization states of the target atom and the incident radiation.
Abstract: The theory of multiphoton ionization for an atomic system of arbitrary complexity is developed using a density matrix formalism. An expression is obtained which determines the differential N-photon ionization cross section as a function of the polarization states of the target atom and the incident radiation. The parameters which characterize the photoelectron angular distribution are related to the general reduced matrix elements for the N-photon transition. Two-photon ionization of unpolarized atoms is treated as an illustration of the use of the theory. The dependence of the multiphoton ionization cross section on the polarization state of the incident radiation, which has been observed in two- and three-photon ionization of Cs, is accounted for by the theory. Finally, the photoelectron spin polarization produced by the multiphoton ionization of unpolarized atoms, like the analogous polarization resulting from single-photon ionization, is found to depend on the circular polarization of the incident radiation.
TL;DR: In this paper, it was shown that photo-electrons emitted from trivalent atoms in a two-photon ionization process are totally polarized if the incident light is of total circular polarization and its wavelength matches the resonance condition for the transition between ground state (n2P12/) and the first excited state(n+1)2S12/.
Abstract: It is argued that photo-electrons emitted from trivalent atoms in a two-photon ionization process are totally polarized if the incident light is of total circular polarization and its wavelength matches the resonance condition for the transition between ground state (n2P12/) and the first excited state (n+1)2S12/. The estimated photoionization yield compares favourably with that of the analogous process in alkali atoms. Some of the most important conditions for a successful experiment are considered.
Patent•
04 Jun 1973
TL;DR: In this paper, a partial-radial-line antenna is designed to radiate elliptically polarized waves characterized by low or near zero db axial ratio (i.e., nearly circular polarization) over entire angular sectors ranging from 60 DEG to 300 DEG.
Abstract: A partial-radial-line antenna comprises a sector of a radial waveguide with the outer edges of its two parallel spaced plates terminating in identical circular arcs which define the antenna aperture. The radial sector is connected at its center or apex to a rectangular-waveguide input transmission line such that the wave excited in the radial sector propagates with its electric or E-field lines extending along circular arcs between the diverging side walls of the same radial waveguide sector. For circularly polarizing the radiated energy, the circularly-shaped antenna aperture is covered by a polarizer, and a plurality of arcuately displaced radial absorption vanes are mounted between and normal to the plates of the radial waveguide sector. The antenna is excited with energy in the TE10 radial line mode such that the E-field lines are circular and emanate from the centered feed point. The E-field is thus perpendicular to all the absorption vanes and to the diverging side walls. With an appropriately designed polarizer, antennas of this type are designed to radiate elliptically polarized waves characterized by low or near zero db axial ratio (i.e., nearly circular polarization) over entire angular sectors ranging from 60 DEG to 300 DEG for a broad frequency band extending over at least an octave.
TL;DR: In this article, the authors measured the ratio of the total two-photon ionization rate for circularly polarized light to that for linearly polarized light, and obtained the ratio for the nP to epsilon S and NP to Epsilon D bound-free radial matrix elements.
Abstract: It is shown that by measuring the ratio of the total two-photon ionization rate for circularly polarized light to that for linearly polarized, one can obtain the ratio of the nP to epsilon S and nP to epsilon D bound-free radial matrix elements. Also discussed is the case of three-photon ionization in which the ratio of the nD to epsilon P and nD to epsilon F bound-free radial matrix elements can be obtained.
TL;DR: In this article, the Stokes parameters were used to characterize the state of the wave in geodesic synchrotron radiation emitted by a charge in an orbit close to the circular photon orbit at 3M around a nonrotating black hole of mass M. The analysis was carried out using Stokes parameter s (sub 2) which completely characterized the wave state.
Abstract: The pattern of geodesic synchrotron radiation emitted by a charge in an orbit close to the circular photon orbit at 3M around a nonrotating black hole of mass M is studied The analysis is carried out using Stokes parameters, which completely characterize the state of the wave The linear polarization, as observed at infinity, is total in the orbital plane and not smaller than 90% at the half-width of the beam At the poles, pure circular polarization would be observed In the region between the orbit plane and the poles the polarization shows features not present in ordinary synchrotron radiation In our model, parameters more sensitive to deviations from the orbital plane are the Stokes parameter s (sub 2) and the tilt angle of the polarization ellipse
Journal Article•
TL;DR: In this paper, the conditions of applicability of the transfer equations for normal waves are found (orthogonality of normal waves or a large phase shift between the waves over a mean free path).
Abstract: The conditions of applicability of the transfer equations for normal waves are found (orthogonality of normal waves or a large phase shift between the waves over a mean free path). Expressions are derived for the degree of orthogonality of normal waves in an axially symmetric medium (magneto-active plasma or gas of atoms experiencing the normal Zeeman effect). Simple formulas for the degree of circular polarization-of radiation emitted by the atmosphere of a star with a strong, dipolelike magnetic field are derived on basis of the equations for the normal wave intensities. The polarization of radiation at large depths of an anisotropic medium is considered and it is pointed out when such polarization may occur. (auth)
TL;DR: In this article, the magnetic circular polarization of the emission produced by A-band excitation in KI:Sn 2+ has been obtained and the unexpected negative polarization can be explained qualitatively by the effect of a charge-compensating vacancy located in the nearest neighbor position.
TL;DR: In this paper, the optical constants of EuO and EuS single crystals were determined at 300 K by means of a Kramers-Kronig analysis of the reflectivity for photon energies up to 12 eV.
Patent•
19 Dec 1973TL;DR: In this paper, an antenna element for use in a phased array antenna is disclosed, which includes a first and a second non-reciprocal quarter-wave plate having field orientations effectively 45° with respect to each other.
Abstract: An antenna element for use in a phased array antenna is disclosed. Such antenna element is a reciprocal device adapted selectively to radiate radio frequency energy of either circular or linear polarization. Such antenna element includes waveguide means for passing radio frequency energy and for radiating such energy; and means adapted to transform the polarization of the radio frequency energy as such passes through the waveguide means to radiate such radio frequency energy selectively with either linear or circular polarization. In a preferred embodiment the just-mentioned means includes a first and a second nonreciprocal quarter-wave plate having field orientations effectively 45° with respect to each other. Such nonreciprocal quarter-wave plates flank a third nonreciprocal quarter-wave plate switchable so that its field orientation is either aligned with the field orientation of the first nonreciprocal quarter-wave plate or, while still aligned as before, turned 180°. Further, the third quarter-wave plate may be switched into a nonenergized state. A reciprocal quarter-wave plate is disposed between the radiating end of the waveguide means and the second nonreciprocal quarter-wave plate. A phase shifter section is disposed between the third nonreciprocal quarter-wave plate and the first nonreciprocal quarter-wave plate. When the field orientations of the first and the third quarter-wave plate are aligned, vertically polarized radio frequency energy introduced into the waveguide means is changed to radiate as horizontally polarized radio frequency energy. When the field orientation of the third quarter-wave plate is reversed by 180°, vertically polarized radio frequency energy introduced into the waveguide means is radiated as vertically polarized radio frequency energy. When the third quarter-wave plate is unenergized, vertically polarized radio frequency energy introduced into the waveguide means is changed to radiate as circularly polarized radio frequency energy. The phase shifter section, whatever the polarization of the radio frequency energy passing through, is operative to change, in accordance with a beam steering control signal, the phase of such energy.
TL;DR: In this paper, the differential and total cross sections for two-photon detachment of H- are computed analytically within the asymptotic model for both linearly and circularly polarized light.
Abstract: The differential and total cross sections for two-photon detachment of H- are computed analytically within the asymptotic model for both linearly and circularly polarized light. The total cross section for unit flux is of the order 10-48 cm2. The differential cross section for linearly polarized light is nearly isotropic near the two-photon absorption threshold but is sharply peaked along the polarization direction just below the threshold for one-photon detachment. The circular polarization efficiency is very small near the two-quantum threshold but is close to its theoretical maximum near the one-quantum threshold.
Journal Article•
TL;DR: In this paper, the inverse Compton scattering of synchrotron radiation has been studied in both the case of optically thin and optically thick sources, and it has been shown that a substantial amount of the linear synchoretron polarization is preserved by inverse Compton effect, though losses of an order up to 75 to 80%.
Abstract: The formulae are given for calculating the linear polarization of the emission due to inverse Compton scattering of synchrotron radiation. Both the cases of optically thin and optically thick (to their own synchrotron emission) sources are studied. Numerical results are also given showing that a substantial amount of the linear synchrotron polarization is preserved by the inverse Compton effect, though losses of an order up to 75 to 80% can often be present. Some applications of these results to astrophysical situations are proposed. The importance of carrying out the same kind of computation for circular polarization is also stressed. (auth)